On June 29, 2012, a devastating line of thunderstorms known as a derecho (deh REY cho) moved east-southeast at 60 miles per hour (mph) from Indiana in the early afternoon to the Mid-Atlantic region around midnight. The states most significantly impacted were Indiana, Ohio, Kentucky, Pennsylvania, West Virginia, Maryland, Virginia, Delaware, New Jersey, and North Carolina, as well as Washington, D.C. Nearly every county impacted by this convective system suffered damages and power outages. Winds were commonly above 60 mph with numerous reports of winds exceeding 80 mph. Some areas reported isolated pockets of winds greater than 100 mph. The storm resulted in 13 deaths, mainly a result of falling trees. One major impact from the derecho was widespread power outages. More than 4 million customers were without power, some for more than a week after the storms moved through. To make matters worse, the area affected was in the midst of a prolonged heat wave. There were 34 heat-related fatalities in areas without power because of the derecho.
3 2. Derecho Science and Climatology A derecho is a complex of thunderstorms or a mesoscale convective system (MCS) that produces large swaths of severe, straight-line wind damage at Earth’s surface. Johns and Hirt (1987) set spatial, temporal, and damage limitations when classifying thunderstorm complexes as derechos. Specifically, for an MCS to be classified as a derecho, the following conditions must be met: • There must be a concentrated area of convectively induced wind damage or gusts greater than or equal to 58 mph occurring over a path length of at least 250 miles. • Wind reports must show a pattern of chronological progression in either a singular swath (progressive; this event was a classic example) or a series of swaths (serial). • There must be at least three reports separated by 64 kilometers (km) or more of Enhanced Fujita 1 (EF1 damage) and/or measured convective wind gusts of 74 mph or greater. • No more than 3 hours can elapse between successive wind damage/gust events. Derechos occur year-round but are most common from May to August (Coniglio et al., 2004). Derechos form in a wide spectrum of large-scale weather patterns and occur in a broad range of air mass instability and low to mid-level wind shear (the change of wind direction and speed with height) environments (Evans and Doswell, 2001). The majority of events fall into three jet stream patterns: • Well-defined approaching upper level disturbance • Upper-level ridge of high pressure • Zonal west to east flow In the last two patterns particularly, the forcing for the development of a derecho can be subtle and difficult to forecast. Forecasters may be aware that a pattern is setting up for a potential derecho, but pinpointing the timing and location of the storms is often problematic because favorable patterns may exist for several days without derecho formation. For progressive derechos, like this event, a west-to-east oriented surface frontal boundary usually exists. The derecho typically initiates on the north side of the boundary as loosely organized elevated thunderstorms, which eventually grow upscale, forming a large bow shaped echo. The bow echo then moves east-southeastward crossing the front into the warm and very unstable air to the south (Johns, 1993). The storm-scale mechanisms governing the upscale growth and the transition from elevated to surface-based storms are not well understood. The demise of derechos tends to occur when they move into an environment of weaker instability and low to mid-level wind shear (Coniglio et al., 2004). Coniglio and Stensrud (2004) developed a climatology of derechos for the eastern half of the United States. Figure 1 displays this derecho climatology for May through August from 1980-2001.
LOSS OF WEATHER RADIOS
Transmitter Date of Outage Date Restored Reason for Outage Manassas, VA June 29, 2012 July 04, 2012 No power or phone lines to site Baltimore, MD June 29, 2012 July 02, 2012 No power or phone lines to site Hagerstown, MD June 29, 2012 July 02, 2012 No power or phone lines to site Frostburg, MD June 29, 2012 July 01, 2012 No power or phone lines to site Fredericksburg, VA June 29, 2012 July 03, 2012 No power or phone lines to site Washington, D.C. June 29, 2012 July 04, 2012 No power or phone lines to site Moorefield, WV June 29, 2012 July 02, 2012 No power or phone lines to site Charlottesville, VA June 29, 2012 June 30, 2012 No power or phone lines to site
Table 2: Power outage data by state provided by FEMA State Number of customers without Power on July 05, 2012 Number of customers without power at peak of outage New Jersey 17,564 135,322 Washington, D.C. 1,000 68,567 Maryland 53,442 899,171 Virginia 89,104 1,076,051 Kentucky 1,000 52,616 Indiana 3,900 135,177 Ohio 139,080 915,366 West Virginia 226,483 643,284
The NWS wants to improve the Warning Language. A Severe Thunderstorm warning to most people mean wind and rain maybee hail. THe issue is this event shows it is an issue that needs to be addressed .. A PDS Particular Dangerous Watch was issued , there needs to be a PDS warning or WIND EMERGENCY ... Language that would say your life is in danger, I will be writing a paper on this subject for the National Weather Association National Meeting